Re: [RFC 05/10] vhost: Add vhost_dev_from_virtio

[Eugenio Perez Martin <eperezma@redhat.com>]

On Mon, Feb 1, 2021 at 7:13 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> On 2021/1/30 上午4:54, Eugenio Pérez wrote:
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > ---
> >   include/hw/virtio/vhost.h |  1 +
> >   hw/virtio/vhost.c         | 17 +++++++++++++++++
> >   2 files changed, 18 insertions(+)
> >
> > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> > index 4a8bc75415..fca076e3f0 100644
> > --- a/include/hw/virtio/vhost.h
> > +++ b/include/hw/virtio/vhost.h
> > @@ -123,6 +123,7 @@ uint64_t vhost_get_features(struct vhost_dev *hdev, const int *feature_bits,
> >   void vhost_ack_features(struct vhost_dev *hdev, const int *feature_bits,
> >                           uint64_t features);
> >   bool vhost_has_free_slot(void);
> > +struct vhost_dev *vhost_dev_from_virtio(const VirtIODevice *vdev);
> >
> >   int vhost_net_set_backend(struct vhost_dev *hdev,
> >                             struct vhost_vring_file *file);
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index 28c7d78172..8683d507f5 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -61,6 +61,23 @@ bool vhost_has_free_slot(void)
> >       return slots_limit > used_memslots;
> >   }
> >
> > +/*
> > + * Get the vhost device associated to a VirtIO device.
> > + */
> > +struct vhost_dev *vhost_dev_from_virtio(const VirtIODevice *vdev)
> > +{
> > +    struct vhost_dev *hdev;
> > +
> > +    QLIST_FOREACH(hdev, &vhost_devices, entry) {
> > +        if (hdev->vdev == vdev) {
> > +            return hdev;
> > +        }
> > +    }
> > +
> > +    assert(hdev);
> > +    return NULL;
> > +}
>
>
> I'm not sure this can work in the case of multiqueue. E.g vhost-net
> multiqueue is a N:1 mapping between vhost devics and virtio devices.
>
> Thanks
>

Right. We could add an "vdev vq index" parameter to the function in
this case, but I guess the most reliable way to do this is to add a
vhost_opaque value to VirtQueue, as Stefan proposed in previous RFC.

I need to take this into account in qmp_x_vhost_enable_shadow_vq too.

>
> > +
> >   static void vhost_dev_sync_region(struct vhost_dev *dev,
> >                                     MemoryRegionSection *section,
> >                                     uint64_t mfirst, uint64_t mlast,
>